The present invention pertains to a working assembly for fire fighting vehicles with aerial boom systems that carry and position a fluid delivery line. Generally, such fire fighting vehicles include a lower boom section and an upper boom section pivotally connected to the lower boom section. The aerial boom system can be actuated to position a fluid nozzle at the end of the upper boom section relative to the exterior of a burning structure to discharge a fire fighting fluid. In those circumstances when an interior of a structure is burning, there may be a need to create an opening through the exterior of the structure to discharge a fire fighting fluid into the interior of the burning structure. There is a need for a fire fighting vehicle that carries a working assembly on the aerial boom system that can be actuated to pierce an exterior surface of a structure to permit a fire fighting fluid to be discharged into the interior of a burning structure.